Separation of barium values from uranyl nitrate solutions



Feb. 24, 1959 Y E. R. TOMPKINS 2,875,024

SEPARATION OF BARIUM VALUES FROM UlfiANYL. NITRATE SOLUTIONS Filed Aug.27, 1946 A ro/away United States Patent SEPARATION OF BARIUM VALUES FROMURANYL NITRATE SOLUTIONS Edward R. Tompkins, Oak Ridge, Tenn., assignorto the United States of America as represented by the United Thisinvention relates to a method of processing material containingradioactive barium values in small amount for the separation of thebarium activity from extraneous matter such as substances of the kindpresent in solutions of neutron irradiated uranium, for example,plutonium values and fission products other than barium values. Moreparticularly, this invention relates to a method of separating tracerquantities of barium activity from solutions containing the same byadsorption and selective elution.

As described herein, the isotope of element 94, having a mass of 239, isreferred to as 94 and is also called plutonium, symbol Pu. In addition,the isotope of element 93 having a mass of 239 is referred to as 93 andis called neptunium, symbol Np. Furthermore, the

term values or its equivalent when employed herein a with reference toan element is intended to embrace the element and compounds thereof. Forexample, the term plutonium values is intended to include plutonium aswell as compounds thereof.

Naturally occurring uranium contains a major portion of U a minorportion of U and small amounts of other substances such as UX and UXWhen a mass of such uranium is subjected to neutron irradiation,particularly with neutrons of resonance or thermal energies, U bycapture of a neutron becomes U which has a half life of abouttwenty-three minutes and by beta decay becomes 93 The 93 has a half lifeof about 2.3 days and by beta decay becomes 94 Thus neutron irradiateduranium contains both 93 and 94 but by storing irradiated uranium for asuitable period of time, the 93 is converted almost entirely to 94 Inaddition to the above mentioned reaction, the reaction of neutrons withfissionable nuclei such as the nucleus of U results in the production ofa large number of radioactive fission products. For example, when anatom of U undergoes fission, two fragments are formed. These fragmentsvary sufliciently in their masses and hence their atomic numbers to givesome 34 elements, all of which initiate further reaction chains with theemission of radiations. These chains are the source of all of theradioactivity that renders isolation of any one of the products ofirradiation of uranium so difiicult. The radiations include; (1) beta orhigh speed negative electrons with variable energy contents, andtherefore, different velocities, (2) soft gamma, or electro-magneticradiation similar to X-rays but with a shorter wave length andmoderately higher energy content, (3) hard gamma similar to the softtype except that it hasa shorter wave length and higher energy content,and (4) neutrons.

In general, the stability of an atom depends on the ratio of protons toneutrons in the nucleus and certain ratios, therefore, result in anexcess energy content that must be emitted as radiation before a stableend product is formed. While most naturally occurring isotopes are icestable and therefore not radioactive, those resulting from fission haveproton-neutron ratios such as to cause mternal instability. As a result,they tend to stabilize and in the process emit their excess energies inone of five general ways. 0

In the first place, an atom may emit a beta particle from the nucleuswhere the only possible source of a negative electron is from a neutronwhich gives both a positive and negative charge. The loss of thenegative charge converts the neutron to a proton and there is a gain ofone in atomic number and hence a transmutation to the next higherelement. Such a change, of course, alters the proton to neutron ratioand may result in a stable atom, although this is not necessarily true.

In the second place, a beta particle of lower energy content may beemitted, thus forming the next higher element while still leaving thenucleus with too great an energy content to be stable. The first betaparticle may then be followed by another one to form the second higherelement in the atomic series which again may or may not be stable.

Thirdly, a beta particle of intermediate energy may be emitted to forman unstable isotope of the next higher element which, due to its excessenergy, may give off a gamma ray rather than a beta particle. Thisprocess may also result in either stable or an unstable atom.

Fourthly, the beta-decay of a fission product may leave the nucleus in astate of excitation higher than the binding energy of a neutron in thatnucleus. The neutron is then immediately emitted, and the rate of decayof the neutron-emitting activity observed is just that of the precedingbeta activity.

Finally, an unstable atom may emit a gamma ray which strikes an electronin one of the inner shells of electrons and ejects it in such acondition that it has some of the properties of the nuclear betaparticle. Since the electron, which in this case is known asphotoelectron, does not originate in the nucleus, there is no change inthe atomic number and the process, like that involved in the emission ofa gamma ray, is known as internal conversion.

With the exception of elements 43 and 61, the fission products formed bythe above discussed reaction are all well known elements with normalchemical properties, the only point of difference between them and thenatural element being that they are composed of unstable isotopes. Asbrought out above, due to their internal instability they either undergotransmutation to other elements or stabilize themselves internally bythe emission of one or more of the previously-mentioned radiations.Consequently, stabilization may involve no change in atomic number or achange of severalunits. The average length of the fission chains, thatis the number of transmutations, is about 3.2 but some may be as long as6. In general, a chain reaction has emitted a total of 25 to 30 m e. v.as radiation by the time it is complete.

The fission of U yields two general types of elements, namely heavy andlight. The light fission products possess atomic numbers between 30 and46 and include radioactive zinc, gallium, germanium, arsenic, selenium,bromine, krypton, rubidium, strontium, yttrium, zirconium, columbium,molybdenum, 43, ruthenium," rhodium, and palladium.

The heavy fission products resulting from neutron irradiation of Upossess atomic numbers ranging from 47 to 63 and include radioactivesilver, cadmium, indium, tin, antimony, tellurium, iodine, xenon,cesium, barium, lanthanum, cerium, praseodymium, neodymium, 61, samariumand europium.

Generally speaking, the irradiation of uranium is conducted under suchconditions as result in the combined amount of neptunium and plutoniumbeing equal to approximately 0.02% by weight of the uranium mass. Theconcentration of the fission products in neutron irradiated uranium isapproximately the same as that of the total of the plutonium andneptunium. However, since many of the fission products are radioactive,they change to other elements at certain fixed rates which arecharacteristic of each fission product. In other words, they have fixeddecay rates. Plutonium, on the other hand, is relatively stable, andsince the fission products have varying decay rates, the concentrationof the initially formed radioactive fission products with respect toplutonium changes substantially during the course of the reaction andparticularly during the storage period which is generally employed afterthe neutron irradiated uranium has been removed from the reaction zone.

The quantities of the various individual radioactive fission productspresent in neutron irradiated uranium are extremely small and aregenerally referred to in the art as tracer quantities."

As used herein, the terms tracer and tracer quantity or theirequivalents are employed as definitive of extremely small amounts ofradioactive materials. For example, radioactive materials inconcentrations of to 10- molar are considered to be tracer quantities.Such extremely small amounts are incapable of identification by ordinarymicro analytical methods, and are, therefore, generally identified bythe radiations emitted therefrom by means of any of the usual countingmechanisms known to the art.

As illustrative of a typical neutron irradiated mass containing fissionproducts the following tables are given:

TABLE A Distribution of beta activity in neutron irradiated uranium foreach fission element as percentage of total TABLE B Distribution ofefiective gamma activity in neutron irradiated uranium for each fissionelement as percentage of total Cooling Time Element 30 Days 60 Days 100Days As illustrative of the method of obtaining the data for the abovetables, the following is given. A mixed fission product solution issubjected to counting and is found to have a total beta activity of453,600 counts/minute/milliliter. To a 1.00 ml. sample is added 20.0 mg.of Ru and by appropriate chemical manipulation the Ru is isolated andpurified. The final precipitate Q metallic Ru weighs 18.0 mg. and gives4950 counts/minute. The chemical yield is therefore and the count,corrected for chemical yield, is 5500 counts/minute or 1.21% of thetotal activity.

From the above tables it can be seen that certain fission products arelisted as both beta emitters and gamma emitters. This situation resultsfrom the presence in neutron irradiated uranium of various isotopes ofthe elements which comprise the fission products. Thus, one isotope ofan element may be a beta emitter while another isotope may be a gammaemitter. Furthermore, and as is more generally the case, certain of theisotopes may emit both types of radiation.

Some members of both the light and heavy groups of fission products maybe readily separated from the neutron irradiated uranium mass in thatthey have been found to have chemical properties similar to the rareearths and can, therefore, be isolated by precipitation under carefullycontrolled conditions with about one hundred times their weight ofcarriers such as lanthanum fluoride, bismuth phosphate, and the like.However, many of the fission products in both groups do not respond tosuch treatment and considerable diiliculty has been experienced not onlyin attempting to separate plutonium values from these fission products,but also in attempting to isolate certain of the fission product valuesin carrier-free radioactive form.

It can be seen from the above discussion that the separation andisolation of the various products formed as a result of the neutronirradiation of uranium is an extremely diflicult task, particularly inview of the fact that extremely small quantities of the individualfission products are present in the materials under treatment. Theproblem is further complicated by the presence of the various isotopesand the fact that the elements, considered to be formed at the time offission, may actually represent conversion products from certain of thefission products which have undergone extremely rapid change; that is,those fission products having extremely short half lives. In thisconnection, approximately isotopes of the fission products involved havebeen identified and about 30% of these have half lives of over eighthours. Fission products have been identified that have half livesranging from about 3 seconds to 10 years.

Since, as pointed out above, the fission product values contained in asolution of neutron irradiated uranium even after a considerable periodof storage exhibit radioactive properties, it is particularlyadvantageous not only to separate these fission product values fromplutonium values, but it is also advantageous in certain instances toisolate certain of the fission product values in carrierfree radioactiveform in that they serve as an excellent source of radioactivity whichmay be utilized, among other things, in various fields such as medicineand metallurgy.

Among the fission product values which it is desirable to isolate isradioactive barium. It has been found that barium is present in theabove described group of radioactive fission products in comparativelylow proportion by weight. Since thepercentage of fission products in theoverall mass is extremely small, it can be readily seen that thequantity of barium present in the overall mass to be treated is such asto be considered a tracer quantity.

It is an object of this invention to provide a new method for theseparation and recovery of barium values.

Another object of this invention is to provide a process for separatingradioactive barium values from an irradiated mass containing plutoniumvalues as well as fission product values other than those of barium.

Still another object of this invention is the provision of a method ofseparating barium values from a solution containing the same byadsorption and selective elution.

It is a further object of this invention to provide an all adsorptionprocess of separating barium values from a solution containing the samewhich process may be conveniently operated under conditions of remotecontrol.

These and other objects will become apparent to the skilled worker inthe art upon becoming familiar with the following description.

I have found that barium values may be recovered in high concentrationfrom solutions containing the same together with material includingfission product values other than barium by a method which comprisespassing the solution through an adsorbent under conditions favoringadsorption of barium values together with other material, selectivelyeluting barium values and certain of the other material present from theadsorbent, passing the resulting eluate through a smaller body ofadsorbent under conditions favoring adsorption of barium values andselectively eluting barium values from the smaller body of adsorbent.

In the practice of my invention a wide variety of adsorbents may beutilized including both inorganic adsorbentssuch as silica gel,diatomaceous earth, or the like-and organic adsorbents-such as activatedcar bon, sulphonated carbonaceous material (zeo-carb),phenol-formaldehyde resins preferably containing free sulphonic acidgroups, and the like. Particularly advantageous results are obtained inthe first portion of the process by the use of ion exchange adsorbents,in which the cation of the adsorbent is exchanged for a similarlycharged ion of the substance to be adsorbed. It has been found that theprocess is particularly effective where the adsorbent used is arelatively inert organic material containing free sulphonic acid groups.Thus, the adsorbent may comprise phenol-formaldehyde resins, lignite,phenol-tannic acid resins, or the like, which contain numerous RSO Rgroups, in which R is an organic group such as a methylene group and inwhich R is hydrogen or a metal ion, although R is preferably H+ or Na Aparticularly satisfactory adsorbent which may be employed is aphenol-formaldehyde condensation product containing methylene sulphonicacid groups (CH SO H). In the adsorption process, the hydrogen of thesulphonic acid group is replaced by a cation of the substance to beadsorbed which thereupon-forms a more or less loosely associatedmolecule with the residue.

As an example of a method by which a sulphonated resin may be prepared,175 parts of l-hydroxybenzene- 4-sulphonic acid are heated together with40 parts of a formaldehyde solution of 30% strength for one-half hour toabout 105 C. Then, further 60 parts of formaldehyde are added and thetemperature is kept for about ten hours at 90 C. A hard black resin isformed which is stable to. water and of conchoidal fracture. This resinis washed with water and ground to a powder. By regeneration with anacid or a solution of common salt, this base-exchanging body regains itsoriginal adsorption capacity.

My invention may be more readily understood by reference to theaccompanying drawing in which the figure is a diagrammatic view of anapparatus which may be utilized in the practice of my invention.

Referring to the drawing, the system comprises feed line 1, controlledby valve 2, which passes into tank 3 to the upper portion of which areconnected line 4, controlled by valve 5, and line 6, controlled by valve7. Passage from the bottom of tank 3 is provided by line 8, controlledby valve 9, which line connects to the upper portion of columncontaining a suitable adsorbent 11. To the upper portion of column 10are also connected line 12, controlled by valve 13, and line 14,controlled by valve 15. Line 16 connects the lower portion of column 10to line 17, controlled by valve 18, and to line 19, controlled by valve20, line 19 passing into header 21 which has connected to the upperportion thereof line 22, controlled by valve 23, and line 24, controlledby valve 25. The bottom of header 21 is connected to the upper portionof column 28 by means of line 26, controlled by valve 27. Column 28contains a suitable adsorbent 29 which may be the same as the adsorbentutilized in column 10 or if desired, may be of a different type. To thetop of column 28 are connected line 30, controlled by valve 31, and line32, controlled by valve 33. The bottom of column 28 has connectedthereto line 34 which connects to line 35, controlled by valve 36, andto line 37, controlled by valve 38.

In view of the extreme radioactivity of the material under treatment inaccordance with my invention, the apparatus diagrammatically illustratedis generally inclosed in a suitable shielding and each of the valvesdesignated above is operated by means of remote control.

In operation of the system described above, the solution containingbarium activity is admitted into the system through line 1 by openingvalve 2. The solution in tank 3 is then adjusted to a condition favoringthe adsorption of barium activity therefrom. For instance, should theconcentration of the solution require adjustment or should the pH of thesolution require adjustment, the necessary reagents may be introducedinto tank 3 through line 6 by opening valve 7. If desired, a pluralityof reagent lines may be included in the system for separatelyintroducing various reagents. Agitation of material in tank 3 may beprovided by means of air introduced through line 4, controlled by valve5, and when the solution has reached the desired condition, the air maybe utilized to force the solution out of tank 3 through line 8,controlled by valve 9.

When the solution has reached the desired condition, valve 9 is opened,and the solution passes through line 8 into column 10 where bariumvalues together with other material such as fission product values areadsorbed upon the adsorbent bed 11. When the solution under treatment isa uranyl nitrate solution, some U0 ion may be adsorbed in column 10. Theunadsorbed material passes through line 16 and 17 to disposal, valve 18being open and valve 20 in line 19 being closed. After allowingsufiicient time for the desired adsorption to take place, elution of UOis accomplished by passing dilute H SO through line 12 controlled byvalve 13, and with valve 20 in line 19 closed and valve 18 in line 17open the eluate from column 10 is passed through lines 16 and 17 todisposal.

Following the elution of UO as indicated above, valve 15 in line 14 isopened to admit into column 10 citric acid at a concentration and pHsufficient to elute from adsorbent 11 barium values together with otherfission product values. While the elution of barium values is beingeffected valve 18 isclosed and valve 20 in line 19 is opened allowingthe eluae from column 10 to pass into header 21. In header 21, the pH ofthe eluate from column 10 is adjusted by the admission of reagentthrough line 22 controlled by valve 23. The solution is also diluted bythe admission of diluent such as water through line 24 controlled byvalve 25. Upon reaching the desired pH and desired dilution, valve 27 isopened to allow the thus conditioned solution to pass through line 26into column 28 wherein adsorption of barium values upon adsorbent 29takes place. In addition to barium values, certain rare earth values areadsorbed in column 28. Citric acid at a pH of approximately 3 isadmitted into column 28 through line 30 by opening valve 31. The citricacid at this concentration selectively elutes the rare earth values thusseparating the bulk of the unwanted gamma emitters from the bariumvalues. The eluate from this elution is withdrawn from the columnthrough line 34 and line 35, valve 36 being open and valve 38 in line 37being closed.

After eluting the undesired material in this manner, valve 36 is closed,valve 38 is opened and citric acid at a pH of approximately 6 isintroduced into the column through line 32 by opening valve 33. Citricacid at this pH selectivity elutes barium from the adsorbent and thebarium values is withdrawn from the column through lines 34 and 37. Theprocess of my invention may be considered to be comprised of threeoperations which are extraction of the barium values from uranylnitrate, con centration and then decontamination. For all practicalpurposes, the concentration and decontamination are carried out nearlysimultaneously. Generally speaking, the dilution which is effected inheader 21 is advantageously carried out under such conditions that thefinal volume of liquid is at least 8 times the volume of the originaleluate from column 10.

In selectively eluting the unwanted fission product values from column28, citric acid at a pH of between 2.3 and 3.5 is advantageouslyemployed. Particularly advantageous results have been obtained at pHs ofapproximately 3. Whereas citric acid at a pH of to 7 may beadvantageously employed as an eluting agent selective for barium.Particularly advantageous results may be obtained in eluting barium withcitric acid at a pH of 6.

Generally speaking, the rate of flow of the various liquids through thesystem is maintained low such as from 1 to ml. per minute per square cm.of adsorbent. Ordinarily the rate of flow of the initial solutionthrough the original column is maintained between 1 to 2 ml. per minuteper square cm. of adsorbent. Generally speaking, the rate of flow ofeluting agents is a bit higher than that of the initial solution.Advantageous results have been obtained by passing the eluting agentsthrough the column at a rate of flow of between 2 ml. per minute persquare cm. to 5 ml. per minute per square cm.

In the practice of my invention, when separating barium values fromuranyl nitrate solutions it is advantageous to maintain theconcentration of free HNO in the solution at less than 0.2 M. Althoughseparation of barium values may be effected from solutions in which thefree HNO concentration is greater than 0.2 M, increase in suchconcentration may cause chemical action on the adsorbent.

While the concentration of the uranyl nitrate solutions which may beprocesssed in accordance with my inven tion may vary, advantageousresults may be obtained by processing a solution having a concentrationof between 5% and Particularly advantageous results have been obtainedin processing solutions containing 10 to 20% by weight of uranylnitrate.

While the temperature at which the process is carried out is alsosubject to variation, generally speaking, particularly advantageousresults may be obtained by operating at normal room temperature. Myinvention may be more readily understood by reference to the followingspecific examples.

EXAMPLE I 5 liters of a 10% uranyl nitrate solution was passed throughan adsorption column containing 1 liter of an ion exchange resincharacterized by having a plurality of --CH SO H groups and having aparticle size of -60 mesh. The rate of flow of the solution through theadsorbent was maintained at 1.4 ml. per minute per square Thereafter 4.0liters of 0.25 M H 80 was passed through the adsorbent at a rate of flowof 3.2 ml. per minute per square cm. Thereafter 0.5 liter of B 0 waspassed through the adsorbent at a rate of flow of 3.2 ml. per minute persquare cm. The combined eluate was analyzed and found to contain 5%uranium sulfate and 1% barium. 3.5 liters of 5% citric acid at a pH of 6was passed through the adsorbent at a rate of flow of containing thesame ion exchange resin as was contained in the liter column. The rateof flow through this column was maintained at 8 ml. per minute persquare cm. Following adsorption of barium values and other fissionproduct values from 0.5% citric acid solution, 800 ml. of 5% citric acidat a pH of 3.1 were passed through the ml. column at a rate of flow of 1ml. per minute per square cm. The eluate was collected, and followingthis elution, 100 ml. of 5% citric acid at a pH of 6 was passed throughthe column and the eluate discarded. Thereafter 150 ml. of 5% citricacid at a pH of 6 was passed through the column at a rate of flow of 1ml. per minute per square cm. and this eluate was collected and combinedwith the eluate resulting from the subsequent passage of 50 ml. of waterat a rate of flow of 2 ml. per minute per sq. cm. This eluate containedabout 90% of the Ba originally present.

EXAMPLE II liters of a 20% uranyl nitrate solution was passed through a77 liter adsorbent bed of a 40-60 mesh ion exchange resin characterizdby having a plurality of --CH SO H groups at a flow rate of 1.5 ml. perminute per square cm. Thereafter the adsorbent was washed with 308liters of 0.25 M H 80 at a flow rate of 3 ml. per minute per square cm.and 77 liters of H 0 at a flow rate of 3 ml. per minute per square cm.The resulting eluate upon analysis contained approximately 5% uraniumsulfate and was discarded to waste. Following this elution, the resinbed was washed with 131 liters of 5% citric acid at a pH of 6, the flowrate being maintained at 3 ml. per minute per square cm. The resultingeluate was discarded and thereafter 139 liters of 5% citric acid at a pHof 6 was passed through the adsorbent bed at a flow rate of 3 ml. perminute per square cm. The resulting eluate was collected and combinedwith the eluate resulting from washing the adsorbent with 77 liters of H0 at a flow rate of 3 ml. per minute per square cm. This citric acideluate was diluted to 0.5% citric acid with H 0 and adjusted to a pH of2.5 with 9 liters of concentrated HCl. The resulting solution ofapproximately 1400 liters of /2 citric acid concentration at a pH of 2.5was passed through a 7.7 liter volume of the same adsorbent as utilizedin the first adsorbent bed at a flow rate of 9 ml. per minute per squarecm. The effluent from the adsorbent was discarded. Thereafter theadsorbent was washed with 5% citric acid at a pH of 3.1. 61.6 liters ofthis solution were passed through the adsorbent at a flow rate of 1 ml.per minute per square cm. Thereafter 8 liters of 5% citric acid at a pHof 6 was passed through the adsorbent bed at a flow rate of 1 ml. perminute per square cm. and the eluate was combined with the 5% citricacid eluate to obtain a rare earth fraction.

16 liters of 5% citric acid at a pH of 6 were passed through theadsorbent bed at the flow rate of 1 ml. per minute per square cm. Theadsorbent bed was then washed with 8 liters of water at a flow rate of 3ml. per minute per square cm. The eluates were combined to obtain afraction containing the bulk of the Ba originally present.

In the practice of my invention, if desired, increased concentration ofbarium values may be obtained by utilizing a plurality of successivelysmaller columns in the concentration and decontamination step. In otherwords, after extraction on the first column, the resulting bariumcontaining eluate from the first column may be passed a number of timesthrough successively smaller columns using a resin bed volume V of thatused in the preceding cycle until the desired reduction of volume isattained.

The process of my invention results in the neater, faster, lessdangerous method of separating barium values in that the system foraccomplishing the separation is more adapted to handling by remotecontrol and is readily assembled.

In the specification and claims the following terms have the followingmeanings.

The term efiiuent or its equivalent is intended to include any materialcoming off of the columns.

The term eluate or its equivalent is intended to include any effluentbearing a desired product from a column.

The term eluating agent or its equivalent is intended to include amaterial which removes adsorbed values from a column.

The term eluting agent or its equivalent is intended moval of componentsfrom the solution. It is to be understood, however, that the inventionis not to be limited in any sense by the theory upon which the processis based and that this term is used as it is generally employed in theart of chromatographic separation.

While the invention has been described with reference to certainparticular embodiments and with reference to certain specific examples,it is to be understood that the invention is not to be limited thereby.Therefore, changes, omissions, and/ or additions may be made withoutdeparting from the spirit of the invention as defined in the appendedclaims which are intended to be limited only as required by the priorart.

I claim:

1. A method of separating barium values from a solution containing thesame which comprises passing said solution through an adsorbent underconditions favoring adsorption of barium values together with othermaterial present in said solution, washing said adsorbent with dilutesulfuric acid to remove at least a portion of said other material,washing said adsorbent with citric acid at a pH of approximately to 7 toremove barium values and at least a portion of remaining other material,adjusting the resulting eluate to a pH of approximately 2.3 to 3.5 anddiluting said eluate, passing said diluted eluate through a secondadsorbent of smaller volume, and selectively eluting said barium valuesfrom said second adsorbent.

2. A method of separating barium values from a solution containinguranium values, barium values, and values of fission products other.than barium, which comprises passing said solution through an ionexchange resin to ad sorb thereon barium values, uranium values andfission product values other than barium values, eluting uranium valuesfrom said resin with dilute sulfuric acid, eluting barium values and atleast a portion of said fission product values other than barium valueswith citric acid at a ph of 6, adjusting the pH of the resulting eluateto about 2.5 with HCl and diluting said eluate at least 8 fold withwater, passing said diluted eluate through a smaller volume of said ionexchange resin to adsorb barium values and at least a portion of theremaining fission product values, eluting said adsorbed remainingfission product values with citric acid at a pH of 3, and eluting bariumvalues from said resin with citric acid at a pH of 6.

3. A method of separating Ba from a uranyl nitrate solution which alsocontains UO and fission product values including rare earth values whichcomprises passing said solution through an ion exchange resin to adsorbthereon UO,++, Ha and fission product values, passing dilute sulfuricacid through said resin to elute therefrom UO passing citric acid at apH of 6 through said resin to elute Ra and at least a portion of saidfission product values including rare earth values, adjusting the pH ofthe resulting eluate to 2.5 and diluting said eluate at least 8 fold,passing said diluted eluate through a smaller volume of said resin toadsorb thereon Ra and rare earth values, eluting said rare earth valueswith citric acid at a pH of 3, and eluting said Ba with citric acid at apH of 6.

4. A method of separating Ba from a uranyl nitrate solution containingthe same together with other material resulting from the fission of Uwhich comprises adjusting the concentration of said solution to between10 and 20% in uranyl nitrate, slowly flowing said solution through anion exchange resin to remove therefrom UO barium values and fissionproduct values, washing said resin with dilute sulfuric acid to removeU0 eluting barium values and at least a portion of said fission productvalues with citric acid at a pH of 6 and adjusting the pH of said citricacid eluate to about 2.5 with HCl, diluting said adjusted eluate atleast 8 fold with water, passing said diluted eluate through about ,4the volume of said ion exchange resin to adsorb barium values and rareearth values, eluting said rare earth values with citric acid at a pH of3 and eluting said barium values with citric acid at a pH of 6.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,875,024 February .24, 1959 Edward R Tompkins It is herebj certifiedthat error appears in the-printed specification of the above numberedpatent requiring correction and that the said Letters Patent should readas corrected below.

Column 6, line 51, for "eluae" read eluate column 9, lines 9 and 10, for"The term 'e'luting agent" or its equivalent is intended moval" read Theterm "adsorption" is utilized in referring to removal e Signed andsealed this 8th day of September 9590 (SEAL) Attest:

KARL H. .IDEINE Attesting Ofiicer ROBERT C. WATSON Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,875,024 February 24, 1959 Edward R. Tompkins It is hereby certifiedthat error appears in the -printed specification of the above numberedpatent requiring correction and that the said Letters Patent should readas corrected below.

Column 6, line 51, [for "eluae" read eluate colmnn 9, lines 9- .end 10,for "The term "eluting agent" or its equivalent is intended moval" readThe term "adsorption" is utilized in referring to removal u Signed andsealed this 8th day of September 1959.,

(SEAL) Attest:

KARL ROBERT c. WATSON Commissioner of Patents Attesting Officer UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,875,024February 24, 1959 Edward R, Tompkins.

It is he-rebfl certified that error appears in the-printed specificationof the above "numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

Column 6, line 51, for "eluae" read he eluate column 9, lines 9 and 10,for "The term e'luting agent" or its equivalent is intended moval" readThe term "adsorption" is utilized in referring to removal Signed andsealed this 8th day of September 1959c (SEAL) Attest:

KARL H,.-AX LINE ROBERT c. WATSON Attesting Oificer Commissioner ofPatents

1. A METHOD OF SEPARATING BARIUM VALUES FROM A SOLUTION CONTAINING THESAME WHICH COMPRISES PASSING SAID SOLUTION THROUGH AN ADSORBENT UNDERCONDITIONS FAVORING ADSORPTION OF BARIUM VALUES TOGETHER WITH OTHERMATERIAL PRESENT IN SAID SOLUTION, WASHING SAID ADSORBENT WITH DILUTESULFURIC ACID TO REMOVE AT LEAST A PORTION OF SAID OTHER MATERIAL,WASHING SAID ADSORBENT WITH CITRIC ACID AT A PH OF APPROXIMATELY 5 TO 7TO REMOVE BARIUM VALUES AND AT LEAST A PORTION OF REMAINING OTHERMATERIAL, ADJUSTING THE RESULTING ELUATE TO A PH OF APPROXIMATELY 2.3 TO3.5 AND DILUTING SAID ELUATE, PASSING SAID DILUTED ELUATE THROUGH ASECOND ADSORBENT OF SMALLER VOLUME, AND SELECTIVELY ELUTING SAID BARIUMVALUES FROM SAID SECOND ADSORBENT.